1. Field of the Invention
The present invention relates to apparatus control, and more particularly to an improved joystick for use in controlling the movement of an apparatus such as a surveillance camera that is extremely durable and that is capable of withstanding considerable operator abuse, while providing comfortable and precise control.
2. Description of the Prior Art
Mouse devices and joystick type controllers are well-known coordinate input devices for computer systems. Joystick devices generally include a rectangularly shaped base from which the joystick shaft protrudes. The shaft may be shifted in an inclined manner in any direction, and an angle detection mechanism is provided in the base to detect the inclined angle and direction along the X and Y axes. The detected angle and direction are then supplied to a computer system. In addition, many joystick devices also provide for rotational movement about the Z-axis by allowing the joystick shaft to be twisted by the user. This rotational or twisting motion about the Z-axis is also detected and transmitted to a computer system. Potentiometers are typically used as the devices for detecting the angle and rotation of the joystick.
Joysticks are widely used in the closed circuit television (CCTV) industry to control the operation and movement of surveillance cameras. An operator monitoring the image from a surveillance camera may desire to move the camera to follow a subject as it moves through the area within the range of the camera. Such tracking typically requires reasonably precise movement of the camera that is accomplished using a computer system that responds to signals generated from an operator controlled joystick. Unexpected movements by the subject being tracked, or a need by the operator to suddenly change the direction of the camera may often result in harsh treatment of the joystick used to control the camera. The useful lives of many existing joysticks are often cut short by such normal operator use (and/or abuse) because the joystick devices are flimsy, poorly constructed, or poorly designed and subject to breakage in a relatively short period of time.
Several joysticks including those described in U.S. Pat. Nos. 4,857,881 and 6,059,660 utilize slotted cross members attached to journals at either end such that the rod of the joystick extends through the slots of each of the cross members. Each of the cross members is attached to a potentiometer. Motion imparted to the joystick along the X-axis imparts rotation to one of the slotted cross members and its associated potentiometer, and motion imparted to the joystick along the Y axis imparts rotation to the other of the slotted cross members and its associated potentiometer. However, neither of such cross members recognizes rotational motion imparted along the Z-axis.
Converting motion imparted along the Z-axis of a joystick has been a particularly troublesome obstacle to joystick design. This is because many existing joysticks cannot withstand excess rotational twisting or turning motion imparted around the Z-axis. Twisting or turning the joystick around the Z-axis is part of the ordinary control it provides. However, even minor over-twisting of a joystick can lead to wrapping and ultimately disconnection of wires leading to the joystick, as well as destruction of, or disconnection of the joystick from the mechanism of cross axes in the joystick base which receive the motion imparted to the joystick by the user. Either situation is unacceptable in that it renders the joystick inoperable. U.S. Pat. No. 6,059,660 begins to address this problem by preventing the joystick shaft from rotating around the Z-axis, and by providing a switch between the joystick handle and the joystick shaft for detecting whether the handle has been rotated using a set of contacts on an intermediate switch. However, there is nothing in this device to prevent unchecked rotation of the joystick handle, and very few contacts are provided on the switch such that considerable rotation around the Z-axis will not be detected at all. Moreover, the contacts themselves do not yield the more precise rotational detection information that can be provided by a potentiometer.
Many existing joysticks such as those described in U.S. Pat. Nos. 3,707,093, 4,825,157, 5,286,024 and 5,738,352 utilize tension springs that are attached to the base or shaft of the joystick. Many such springs are expanded as the joystick is moved. The tension in the spring pulls the joystick back to a “home” position when the joystick is released. Many such tension springs suffer from the drawbacks of being easily disconnected from their supports, and from wearing out after constant use.
Other joysticks have potentiometers that are adjustably mounted with respect to the rotational axes of the base, allowing for fine tuning depending upon the position of the joystick itself. However, after the adjustments have been made, over time the adjustable mounting structures tend to become loose, thereby affecting the signals generated by the potentiometers, and skewing the control of the joystick.
Grease or other lubrication is also required in a number of existing joysticks devices on their lower axes as well as at the bottom of the joystick shaft where it attaches to the support base. Such lubricants may cause problems in that they may spread onto the joystick itself making it greasy, repulsive and difficult to control.
For all of these above reasons, and others, it is desirable to provide a durable, reliable and comfortable joystick that is capable of withstanding substantial rotational motion imparted along the Z-axis without failure, while also providing a high level of precision necessary for use in controlling a surveillance camera, and for other applications requiring similar precision.